<%@ page import="java.util.ArrayList" %>
<%@ page import="java.util.HashMap" %><%--
  Created by IntelliJ IDEA.
  User: WIzarder
  Date: 2021/5/31
  Time: 16:06
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <%
        // 1、值为 null 值的时候，为空
        request.setAttribute("emptyNull",null);
        // 2、值为 空串 值的时候，为空
        request.setAttribute("emptyStr","");
        // 3、值为 空的Object数组 值的时候，为空
        request.setAttribute("emptyObj",new Object[]{});
        // 4、值为 空的List值的时候，为空
        request.setAttribute("emptyList",new ArrayList<Object>());
        // 5、值为 空的Map值的时候，为空
        request.setAttribute("emptyMap",new HashMap<String,Object>());
    %>
        ${empty emptyNull}<br/>
        ${empty emptyStr}<br/>
        ${empty emptyObj}<br/>
        ${empty emptyList}<br/>
        ${empty emptyMap}<br/>
        ${true?"你好呀":123}
</body>
</html>
